Human Rights Watch on Wednesday called on the government to drop insurrection charges against 11 opposition activists, including one who holds a US passport.

The group called the charges “ridiculous,” in a statement released the day before the Phnom Penh municipal court is set to hear their case.

“The prosecution of the 11 activists is the latest round of Prime Minister Hun Sen’s campaign to intimidate and imprison opponents of his government,” Brad Adams, Asia director for the group, said in the statement.

Six of 11 activists of the Cambodia National Rescue Party have been released on bail, but five of them remain in detention, including US citizen Meach Sovannara, who runs the Rescue Party’s media center.